Configuring optical layers in imprint lithography processes

ABSTRACT

An imprint lithography method of configuring an optical layer includes imprinting first features of a first order of magnitude in size on a side of a substrate with a patterning template, while imprinting second features of a second order of magnitude in size on the side of the substrate with the patterning template, the second features being sized and arranged to define a gap between the substrate and an adjacent surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the filing date of U.S.Provisional Application No. 62/429,214, filed on Dec. 2, 2016. Thecontents of U.S. Application No. 62/429,214 are incorporated herein byreference in their entirety.

TECHNICAL FIELD

This invention relates to configuring optical layers in imprintlithography processes, and more particularly to forming features ofdifferent orders of magnitude in size on a substrate in one processingstep.

BACKGROUND

Nanofabrication (e.g., nanoimprint lithography) can include thefabrication of very small structures that have features on the order of100 nanometers or smaller. One application in which nanofabrication hashad a significant impact is in the processing of integrated circuits.The semiconductor processing industry continues to strive for largerproduction yields, while increasing a number of circuits formed on asubstrate per unit area of the substrate. To this end, nanofabricationhas become increasingly important to achieving desired results in thesemiconductor processing industry. Nanofabrication provides greaterprocess control while allowing continued reduction of minimum featuredimensions of structures formed on substrates. Other areas ofdevelopment in which nanofabrication has been employed includebiotechnology, optical technology, mechanical systems, and the like. Insome examples, nanofabrication includes fabricating structures onsubstrates that are assembled to form an optical device.

SUMMARY

The invention involves a realization that improvements in imprintingthree-dimensional (3D) patterns on substrates can increase an accuracyand a precision, while reducing a cost and a complexity associated withproducing such patterns. Conventional imprint lithography processes mayinclude imprinting a nano-scale pattern on a substrate in a first stepand subsequently imprinting features of a larger order of magnitude onthe substrate in a second, subsequent step. For such processes, cleaningand treating of the nano-scale pattern may be required prior to formingthe larger features, which is associated with additional costs andadditional time. Furthermore, aspects of forming the larger features inthe subsequent step can sometimes jeopardize a mechanical integrityand/or a functional integrity of the nano-patterned substrate. In thisregard, various aspects of disclosed imprint lithography methods canallow imprinting of 3D structures with features that have differentorders of magnitudes with multiple functions (e.g., any of opticalfunctions, anti-reflective, and spacing) in a single imprinting step.Such methods yield precise, accurate structures at a reduced cost andduration, as compared to alternative methods.

One aspect of the invention features an imprint lithography method ofconfiguring an optical layer. The imprint lithography method includesimprinting first features of a first order of magnitude in size on aside of a substrate with a patterning template, while imprinting secondfeatures of a second order of magnitude in size on the side of thesubstrate with the patterning template, wherein the second features aresized and arranged to define a gap between the substrate and an adjacentsurface.

In some embodiments, imprinting the first features includes forming oneor both of diffraction gratings and anti-reflective features on the sideof the substrate.

In certain embodiments, imprinting the second features includes formingspacers on the side of the substrate.

In some embodiments, the method further includes imprinting one or bothof the spacers and the anti-reflective features along a peripheral edgeof the side of the substrate.

In certain embodiments, the method further includes imprinting one orboth of the spacers and the anti-reflective features within an interiorregion of the side of the substrate.

In some embodiments, the side of the substrate is a first side of thesubstrate, and the imprint lithography method further includesimprinting third features of the first order of magnitude in size on asecond side of the substrate.

In certain embodiments, imprinting the third features includes formingdiffraction gratings or anti-reflective features on the second side ofthe substrate.

In some embodiments, the second order of magnitude in size is greaterthan the first order of magnitude in size.

In certain embodiments, the first order of magnitude in size is of anano-scale, and the second order of magnitude in size is of amicro-scale.

In some embodiments, the method further includes imprinting the secondfeatures on opposite sides of the first features.

In certain embodiments, the method further includes creating thepatterning template from a predecessor mold.

In some embodiments, the method further includes forming deep featuresof the second order of magnitude in size in the predecessor mold.

In certain embodiments, the method further includes forming shallowfeatures of the first order of magnitude in size in the predecessormold.

In some embodiments, the substrate is a first substrate, and theadjacent surface is defined by a second substrate.

In certain embodiments, the method further includes aligning the firstand second substrates with each other.

In some embodiments, the method further includes dispensing an adhesivesubstance atop the second features imprinted on the side of the firstsubstrate.

In certain embodiments, the method further includes attaching the firstand second substrates to each other at the adhesive substance atop thesecond features imprinted on the side of the first substrate to form thegap between the first substrate and the adjacent surface defined by thesecond substrate.

In some embodiments, the method further includes attaching the first andsecond substrates to each other at the adhesive substance atop thesecond features imprinted on the side of the first substrate to form amulti-layer optical device.

In certain embodiments, the method further includes defining a layer ofair between the first and second substrates with a thickness that isdetermined by heights of the second features.

In some embodiments, the gap provides a low index region.

In certain embodiments, the low index region is air with an index ofrefraction of 1.

In some embodiments, the imprint lithography method further includesproviding the multi-layer optical device with layers characterized byalternating indexes of refraction.

Another aspect of the invention features an optical layer that includesa substrate and a pattern imprinted on a side of the substrate with apatterning template. The pattern includes first features of a firstorder of magnitude in size and second features of a second order ofmagnitude in size. The second features are sized and arranged to definea gap between the substrate and an adjacent surface.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,aspects, and advantages of the invention will be apparent from thedescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an imprint lithography system.

FIG. 2 is diagram of patterned layer formed by the imprint lithographysystem of FIG. 1.

FIG. 3 is a top view of an optical layer.

FIG. 4 is a side view of the optical layer of FIG. 3.

FIG. 5 is a top view of an optical layer with a configuration that isdifferent from the configuration of the optical layer shown in FIG. 3.

FIG. 6 is a top view of an optical layer with a configuration that isdifferent from the configurations of the optical layers shown in FIGS. 3and 5.

FIG. 7 is an exploded perspective view of a portion of an optical devicethat includes the optical layer of FIG. 3.

FIG. 8 is a side view of the portion of the optical device of FIG. 7.

FIG. 9 is a diagram illustrating a series of steps for creating apatterning mold that can be used to produce the optical layer of FIG. 3.

FIG. 10 is a side view of spacers formed with the patterning mold ofFIG. 9.

FIG. 11 is a perspective view of the spacers of FIG. 10.

FIG. 12 is a side view of an optical layer with a configuration that isdifferent from the configuration of the optical layer shown in FIGS. 3and 4.

FIG. 13 is a side view of an optical layer with a configuration that isdifferent from the configurations of the optical layers shown in FIGS.3, 4, and 12.

FIG. 14 is a flow chart of an example process for configuring an opticallayer in an imprint lithography process.

Like reference symbols in the various figures indicate like elements.

In some examples, illustrations shown in the drawings may not be drawnto scale.

DETAILED DESCRIPTION

An imprint lithography process for configuring an optical layer isdescribed below. The imprint lithography process involves imprinting amulti-functional structure including features of different orders ofmagnitude from a single template. Such a process can improve a precisionand an accuracy and reduce a cost and a complexity associated withproducing such structures for creating multi-layer optical devices.

FIG. 1 illustrates an imprint lithography system 100 that is operable toform a relief pattern on a top surface 103 of a substrate 101 (e.g., awafer). The imprint lithography system 100 includes a support assembly102 that supports and transports the substrate 101, an imprintingassembly 104 that forms the relief pattern on the top surface 103 of thesubstrate 101, a fluid dispenser 106 that deposits a polymerizablesubstance upon the top surface 103 of the substrate 101, and a robot 108that places the substrate 101 on the support assembly 102. The imprintlithography system 100 also includes one or more processors 128 that canoperate on a computer readable program stored in memory and that are incommunication with and programmed to control the support assembly 102,the imprinting assembly 104, the fluid dispenser 106, and the robot 108.

The substrate 101 is a substantially planar, thin slice that istypically made of one or more materials including silicon, silicondioxide, aluminum oxide, sapphire, germanium, gallium arsenide (GaAs),an alloy of silicon and germanium, indium phosphide (InP), or otherexample materials. The substrate 101 typically has a substantiallycircular or rectangular shape. The substrate 101 typically has adiameter in a range of about 50 mm to about 200 mm (e.g., about 65 mm,about 150 mm, or about 200 mm) or a length and a width in a range ofabout 50 mm to about 200 mm (e.g., about 65 mm, about 150 mm, or about200 mm). The substrate 101 typically has and a thickness in a range ofabout 0.2 mm to about 1.0 mm. The thickness of the substrate 101 issubstantially uniform (e.g., constant) across the substrate 101. Therelief pattern is formed as a set of structural features (e.g.,protrusions and suction structures) in the polymerizable substance uponthe top surface 103 of the substrate 101, as will be discussed in moredetail below.

The support assembly 102 includes a chuck 110 that supports and securesthe substrate 101, an air bearing 112 that supports the chuck 110, and abase 114 that supports the air bearing 112. The base 114 is located in afixed position, while the air bearing 112 can move in up to threedirections (e.g., x, y, and z directions) to transport the chuck 110(e.g., in some instances, carrying the substrate 101) to and from therobot 108, the fluid dispenser 106, and the imprinting assembly 104. Insome embodiments, the chuck 110 is a vacuum chuck, a pin-type chuck, agroove-type chuck, an electromagnetic chuck, or another type of chuck.

Still referring to FIG. 1, the imprinting assembly 104 includes aflexible template 116 with a patterning surface defining an originalpattern from which the relief pattern is formed complementarily on thetop surface 103 of the substrate 101. Accordingly, the patterningsurface of the flexible template 116 includes structural features suchas protrusions and recesses. The imprinting assembly 104 also includesmultiple rollers 118, 120, 122 of various diameters that rotate to allowone or more portions of the flexible template 116 to be moved in the xdirection within a processing region 130 of the imprint lithographysystem 100 to cause a selected portion of the flexible template 116 tobe aligned (e.g., superimposed) with the substrate 101 along theprocessing region 130. One or more of the rollers 118, 120, 122 areindividually or together moveable in the vertical direction (e.g., the zdirection) to vary a vertical position of the flexible template 116 inthe processing region 130 of the imprinting assembly 104. Accordingly,the flexible template 116 can push down on the substrate 101 in theprocessing region 130 to form an imprint atop the substrate 101. Anarrangement and a number of the rollers 118, 120, 122 can vary,depending upon various design parameters of the imprint lithographysystem 100. In some embodiments, the flexible template 116 is coupled to(e.g., supported or secured by) a vacuum chuck, a pin-type chuck, agroove-type chuck, an electromagnetic chuck, or another type of chuck.

In operation of the imprint lithography system 100, the flexibletemplate 116 and the substrate 101 are aligned in desired vertical andlateral positions by the rollers 118, 120, 122 and the air bearing 112,respectively. Such positioning defines a volume 124 within theprocessing region 130 between the flexible template 116 and thesubstrate 101. The volume 124 can be filled by the polymerizablesubstance once the polymerizable substance is deposited upon the topsurface 103 of the substrate 101 by the fluid dispenser 106, and thechuck 110 (e.g., carrying the substrate 101) is subsequently moved tothe processing region 130 by the air bearing 112. Accordingly, both theflexible template 116 and the top surface 103 of the substrate 101 canbe in contact with the polymerizable substance in the processing region130 of the imprint lithography system 100. Example polymerizablesubstances may be formulated from one or more substances, such asisobornyl acrylate, n-hexyl acrylate, ethylene glycol diacrylate,2-hydroxy-2-methyl-1-phenyl-propan-1-one,(2-Methyl-2-Ethyl-1,3-dioxolane-4-yl)methyl acrylate, hexanedioldiacrylate,2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone,diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide,2-hydroxy-2-methyl-1-phenyl-1-propanone, and various surfactants.Example techniques by which the polymerizable substance may be depositedatop the substrate 101 by the fluid dispenser 106 include drop dispense,spin-coating, dip coating, chemical vapor deposition (CVD), physicalvapor deposition (PVD), thin film deposition, thick film deposition, andother techniques. In some examples, the polymerizable substance isdeposited atop the substrate 101 in multiple droplets.

The printing system 104 includes an energy source 126 that directsenergy (e.g., broadband ultraviolet radiation) towards the polymerizablesubstance atop the substrate 101 within the processing region 130.Energy emitted from the energy source 126 causes the polymerizablesubstance to solidify and/or cross-link, thereby resulting in apatterned layer that conforms to a shape of the portion of the flexibletemplate 116 in contact with the polymerizable substance in theprocessing region 130.

FIG. 2 illustrates an example patterned layer 105 formed on thesubstrate 101 by the imprint lithography system 100. The patterned layer105 includes a residual layer 107 and multiple features includingprotrusions 109 extending from the residual layer 107 and recessions 111formed by adjacent protrusions 109 and the residual layer 107.

While the imprint lithography system 100 is described and illustrated asa roll-to-plate or plate-to-roll system, imprint lithography systems ofa different configurations can also be used to produce the examplepatterned layer 105 and the example patterns discussed below. Suchimprint lithography systems may have a roll-to-roll or a plate-to-plateconfiguration.

In some embodiments, a substrate (e.g., the substrate 101 of the imprintlithography system 100) is processed (e.g., imprinted on one or bothsides and cut out to shape) to form an optical layer of a multi-layeroptical device (e.g., a wearable eyepiece, an optical sensor, or anoptical film, such as that used in a display). For example, FIGS. 3 and4 illustrate a top view and a side view, respectively, of an opticallayer 200 that includes a substrate 202, a functional pattern 204imprinted on the substrate 202, and an auxiliary pattern 206 imprintedon the substrate 202. The substrate 202 may be laser cut from a largersubstrate (e.g., the substrate 101) and is provided as a layer oftransparent or semi-transparent plastic (e.g., flexible) or glass (e.g.,rigid) that is made of one or more organic or inorganic materials, inaccordance with the various material formulations described above withrespect to the substrate 101. The substrate 202 has a maximum length ofabout 10 mm to about 500 mm and a maximum width of about 10 mm to about500 mm. The substrate 202 has a relatively high refractive index in arange of about 1.6 to about 1.9 and a transmissivity in a range of about80% to about 95%.

The functional pattern 204 is imprinted atop an upper side 208 of thesubstrate 202 and is located along an interior region 218 with respectto a peripheral edge 216 of the substrate 202. The functional pattern204 is a waveguide pattern formed of multiple diffraction gratings thatprovide a basic working functionality of the optical layer 200. Thediffraction gratings have dimensions in a range of about 10 nm to about500 nm. The diffraction gratings are configured to project light ofwavelengths within a particular range and to focus a virtual image at aparticular depth plane. The focused light, together with focused lightprojected through proximal optical layers, forms a multi-color virtualimage over one or more depth planes. The transmitted light may be redlight with wavelengths in a range of about 560 nm to about 640 nm, greenlight with wavelengths in a range of about 490 nm to about 570 nm, orblue light with wavelengths in a range of about 390 nm to about 470 nm.The diffraction gratings can include multiple combinations andarrangements of protrusions and recessions (e.g., such as theprotrusions 109 and the recessions 111) that together provide desiredoptical effects. The diffraction gratings include in-coupling gratings220 and form an orthogonal pupil expander region 222 and an exit pupilexpander region 224. The functional pattern 204 has a total length ofabout 10 mm to about 500 mm and a total width of about 10 mm to about500 mm.

The auxiliary pattern 206 is imprinted atop the upper side 208 of thesubstrate 202 and surrounds the functional pattern 204. The auxiliarypattern 206 is also co-located with the interior region 218 of thesubstrate 202. The auxiliary pattern 206 includes both anti-reflectivefeatures 210 of a nano-scale and spacers 212 of a micro-scale that maybe distributed in various quantities and arrangements across theauxiliary pattern 206. The auxiliary pattern 206 coincides with theinterior region 218 of the substrate 202 and has a total length of about10 mm to about 500 mm and a total width of about 10 mm to about 500 mm.

The anti-reflective features 210 may be arranged anywhere within theauxiliary pattern 206. The anti-reflective features 210 are sized (e.g.,having a height of less than or equal to about 300 nm and a pitch ofabout 50 nm to about 150 nm) and shaped to reduce surface reflection atthe side (e.g., the upper side 208) of the substrate 202 on which theanti-reflective features 210 are imprinted. For example, theanti-reflective features 210 may reduce the surface reflection of thesubstrate 202 by about 1.0% to about 4.5%. The anti-reflective features210 are further sized and shaped to increase the transmissivity of thesubstrate 202 to greater than about 98.5% (e.g., for a plastic substrate202) and up to about 99.5% (e.g., for a glass substrate 202). Theanti-reflective features 210 are also sized and shaped to provide thesubstrate 202 with a new effective refractive index in a range of about1.2 to about 1.4. Additionally, the anti-reflective features 210 canintroduce birefringence to diminish or enhance refraction of certainlight wavelengths transmitted through the substrate 202.

The spacers 212 are sized to produce a gap (e.g., a layer of air)between the optical layer 200 and an adjacent optical layer thattogether form a part of a multi-layer stacked optical device when thetwo optical layers are adhered to one another, as will be discussed inmore detail below with respect to FIGS. 7 and 8. The spacers 212 may bearranged anywhere within the auxiliary pattern 206 as necessary toprovide adequate structural support for the substrate 202 and for anadjacent optical layer that is in contact with the spacers 212. In someembodiments, the spacers 212 (e.g., in a cured state) have a modulus ofelasticity that is greater than 1 GPa. The spacers 212 can be imprintedin a pre-defined geometry (e.g., tetrahedral, cylindrical, conical,etc.) and therefore may have a cross-sectional shape that is circular,rectangular, etc. The spacers 212 may have a lateral dimension (e.g., awidth or a diameter) in a range of about 1 μm to about 100 μm and avertical dimension (e.g., a height) of about 1 μm to about 50 μm. Eachspacer 212 may be located about 5 μm to about 100 μm from anotheradjacent spacer 212, from an anti-reflective feature 210, or from adiffraction grating of the functional pattern 204.

Other arrangements of functional patterns and auxiliary patterns arepossible. For example, FIG. 5 illustrates a top view of an optical layer300 that includes the substrate 202 and the functional pattern 204 ofthe optical layer 200, as well as an auxiliary pattern 306. Thefunctional pattern 204 is imprinted atop the upper layer 208 of thesubstrate 202, as in the optical layer 200. The auxiliary pattern 306 isalso imprinted atop the upper layer 208 of the substrate 202 and issubstantially similar in construction and function to the auxiliarypattern 206, except that the auxiliary pattern 306 extends across theinterior region 218 to the peripheral edge 216 of the substrate 202.

In another example embodiment, FIG. 6 illustrates a top view of anoptical layer 400 that includes the substrate 202 and the functionalpattern 204 of the optical layer 200, as well as an auxiliary pattern406. The functional pattern 204 is imprinted atop the upper layer 208 ofthe substrate 202, as in the optical layer 200. The auxiliary pattern406 is also imprinted atop the upper layer 208 of the substrate 202 andis substantially similar in construction and function to the auxiliarypattern 206, except that the auxiliary pattern 406 is imprinted alongthe peripheral edge 216 of the substrate 202, such that the interiorregion 218 of the substrate 202 remains non-patterned and surrounds thefunctional pattern 204. In other embodiments, optical layers may includefunctional patterns and auxiliary patterns with different shapes and/orarrangements not shown in the example optical layers 200, 300, 400.

FIG. 7 illustrates an exploded perspective view of a portion of anoptical device 500 (e.g., a wearable eyepiece) that includes multipleoptical layers, including three of the example optical layers 200. FIG.8 illustrates a (non-exploded) side view of the same portion of theoptical device 500. The optical device 500 includes additional opticallayers that are not shown. Referring to FIGS. 7 and 8, the opticaldevice 500 is formed by aligning the optical layers 200 with one anotherand adhering the optical layers 200 to one another with adhesive dropsdispensed atop the spacers 212. The optical layers 200 are subsequentlyfurther adhered to each other with a seal that serves as an attachmentmechanism to which all of the peripheral edges 216 of the optical layers200 are joined. The optical device 500 can include multiple of any ofthe optical layers 200, 300, 400, and other optical layers, and caninclude from 3 to 20 optical layers in total.

For each optical layer 200 in the optical device 500, the spacers 212together form a spacer layer that creates a gap 530 defining a layer ofair between adjacent optical layers 200, as shown in FIG. 8. The layersof air defined by the spacers 212 have a low index of refraction in arange of about 1.0 to about 1.2. The low index layers of air,alternating with the high index optical layers 200, enhances 3Dvisualization and reduces or eliminates coupling of light betweenadjacent optical layers 200. The support structure formed by thearrangement of spacers 212 supports the substrate 202 on which thespacers 212 are imprinted and the adjacent substrate 202 in a way thatprevents or reduces warping of the substrates 202 that may otherwiseoccur if the optical layers 200 were to be adhered via a differenttechnique, such as dispensing drops of glue within interior portions oralong the peripheral edges 216 of the substrates 202.

FIG. 9 illustrates a series of steps for creating a patterning mold 600(e.g., such as the patterning surface provided by the flexible template116) from a predecessor mold 642 (e.g., a non-featured mold). Thepatterning mold 600 defines both shallow features 644 of a nano-scaleand deep features 646 of a micro-scale. Accordingly, the shallowfeatures 644 can be used to form the diffraction gratings of thefunctional pattern 204 and the anti-reflective features 210 of theauxiliary pattern 206 on the substrate 202, while the deep features 646can be used to form the spacers 212 on the substrate 202 in a singleimprinting step, as will be discussed in more detail below with respectto FIG. 14.

In a first step (a) for creating the patterning mold 600, the deepfeatures 646 are formed in the predecessor mold 642 via a course methodto create a micro-featured mold 648. Example course methods includelithography and reactive ion etching. In a next step (b), apolymerizable substance 650 is deposited atop the micro-featured mold648 and patterned with fine features 652 of a nano-scale that projectfrom a residual layer 654 in the manner as described above with respectto FIGS. 1 and 2. In a next step (c), the residual layer 654 is removed,and the fine features 652 are processed to form the shallow features 644in the micro-featured mold 648 via plasma-based dry etching, reactiveion etching, or wet KOH etching of silicon to form the patterning mold600. The spacers 212 produced with the deep features 646 of thepatterning mold 600 are produced with an improved precision and accuracyas compared to spacer features that can be produced with othertechniques that involve dispensing substances to form spacer featuresfor adhering adjacent optical layers. In this regard, heights of thespacers 212 produced from the deep features 646 exhibit goodco-planarity (e.g., to within a tolerance of +/−100 nm across a span ofabout 50 mm), and widths or diameters of the spacers 212 are consistentto within a +/−100 nm tolerance. As a result, the spacers 212 that areformed on the substrates 202 by the deep features 646 of the patterningmold 600 provide the spacer layers with an improved uniformity inthickness across single spacer layers such that adjacent substrates 202can be aligned and oriented accurately and with reduced or eliminatedwarping. Additionally, an accuracy of the widths of the deep features646 advantageously allows for improved structural integrity andfunctional integrity along the interior regions 218 of the substrates202 according to use of the spacers 212, as compared to use of dispenseddrops of glue, which tend to cause warping of substrates, sometimes lacksufficient adhesiveness, and tend to spread into functional patternsimprinted on the substrates. Furthermore, dispensed glue drops may spana relatively large area (e.g., about 500 μm in diameter) across asubstrate with a spacer height of about 25 μm, whereas the spacers 212may span a limited area (e.g., about 10 μm to about 20 μm in diameter)across a substrate with a spacer height of about 25 μm.

FIGS. 10 and 11 respectively illustrate side and perspective views ofspacers 212 of the auxiliary pattern 206 that are formed by the deepfeatures 646 of the patterning mold 600. In the examples of FIGS. 10 and11, the spacers 212 have a generally cylindrical shape and have features(e.g., heights and effective diameters) in a range of about 5 μm toabout 100 μm.

While the optical layer 200 has been described and illustrated as havingthe functional pattern 204 and the auxiliary pattern 206 imprinted on asingle side (e.g., the upper side 208) of the substrate 202, otherconfigurations are possible. For example, FIG. 12 illustrates a sideview of an optical layer 700 that includes the substrate 202 and thefunctional pattern 204 of the optical layer 200 imprinted atop the upperside 208 of the substrate 202, as well as an auxiliary pattern 706imprinted on the lower side 214 of the substrate 202. The auxiliarypattern 706 is substantially similar in construction and function to theauxiliary pattern 206, except that the auxiliary pattern 706 has adifferent size and shape than a size and a shape of the auxiliarypattern 206. For example, the auxiliary pattern 706 includesanti-reflective features 710 located opposite the functional pattern 204and that span a width that is larger than a total width of a span of theanti-reflective features 210 of the auxiliary pattern 206. The auxiliarypattern 706 further includes spacers 712 located on opposite sides ofthe anti-reflective features 710. Owing to the functional pattern 204and the auxiliary pattern 706 being located on opposite sides of thesubstrate 202, the functional pattern 204 and the auxiliary pattern 706are patterned on the substrate 202 in separate imprinting steps, asopposed to being patterned in a single imprinting step, as is the casefor the optical layer 200. Accordingly, a patterning mold with finefeatures and deep features that correspond to a configuration of theauxiliary pattern 706 can be created for forming the auxiliary pattern706 in a manner similar to that described above with respect to thepatterning mold 600. A separate patterning mold with fine features thatcorrespond to a configuration of the functional pattern 204 can becreated for forming the functional pattern 204.

In another example, FIG. 13 illustrates a side view of an optical layer800 that includes the substrate 202 and the functional pattern 204 ofthe optical layer 200 imprinted atop the upper side 208 of the substrate202, as well as a first auxiliary pattern 806 imprinted atop the upperside 208 of the substrate 202 and a second auxiliary pattern 860imprinted on the lower side 214 of the substrate 202. For example, thefirst auxiliary pattern 806 includes spacers 812 located on oppositesides of the functional pattern 204. The second auxiliary pattern 860includes anti-reflective features 810 located opposite the functionalpattern 204. Accordingly, a patterning mold with fine features and deepfeatures that correspond to a configuration of the functional pattern204 and the first auxiliary pattern 806 can be created for forming thefunctional pattern 204 and the first auxiliary pattern 806 in a singleimprinting step in a manner similar to that described above with respectto the patterning mold 600. A separate patterning mold with finefeatures that correspond to a configuration of the second auxiliarypattern 860 can be created for forming the second auxiliary pattern 860.Owing to the functional pattern 204 and the first auxiliary pattern 806being located on a side of the substrate that is opposite a side thesubstrate 202 on which the second auxiliary pattern 860 is located, thefunctional pattern 204 and the first auxiliary pattern 806 are patternedon the substrate 202 together in one imprinting step, and the secondauxiliary pattern 860 is patterned on the substrate 202 in anotherimprinting step.

FIG. 14 displays a flow chart of an example process 900 for configuringan optical layer (e.g., the optical layer 200, 300, 400) in an imprintlithography process. First features of a first order of magnitude insize are imprinted on a first side (e.g., the upper side 208 or thelower side 214) of a substrate (e.g., the substrate 202) with apatterning template (e.g., the patterning mold 600) (902). The firstfeatures may include one or both of diffraction gratings (e.g., thediffraction gratings provided by the functional pattern 204) andanti-reflective features (e.g., the anti-reflective features provided bythe auxiliary patterns 206, 306, 406). Second features of a second orderof magnitude in size are imprinted on the first side of the substratewith the patterning template while the first features are imprinted onthe first side of the substrate with the patterning template, where thesecond features are sized and arranged to define a gap (e.g., the gap530) between the substrate and an adjacent surface (e.g., a side of anadjacent substrate) (904). The second features may include spacers(e.g., spacers provided by the auxiliary patterns 206, 306, 406). Insome examples, one or both of the spacers and the anti-reflectivefeatures are imprinted along a peripheral edge (e.g., the peripheraledge 216) of the first side of the substrate. In some examples, one orboth of the spacers and the anti-reflective features are imprinted alongan interior region (e.g., the interior region 218) of the first side ofthe substrate. In some examples, the second features are imprinted onopposite sides of (e.g., around) the first features.

The second order of magnitude in size is greater than the first order ofmagnitude in size. In some examples, the first order of magnitude insize is of a nano-scale, and the second order of magnitude in size is ofa micro-scale. In some embodiments, the process further includesimprinting third features of the first order of magnitude in size on asecond side (e.g., the upper side 208 or the lower side 214) of thesubstrate. The third features may include diffraction gratings oranti-reflective features.

In some embodiments, the process further includes creating thepatterning template from a predecessor mold (e.g., the predecessor mold642). In some embodiments, the process further includes forming deepfeatures (e.g., the deep features 646) of the second order of magnitudein size in the predecessor mold. In some embodiments, the processfurther includes forming shallow features (e.g., the shallow features644) of the first order of magnitude in size in the predecessor mold.

In some examples, the substrate is a first substrate, and the adjacentsurface is defined by a second substrate. In some embodiments, theprocess further includes aligning the first and second substrates witheach other. In some embodiments, the process further includes dispensingan adhesive substance (e.g., a drop of glue) atop the second featuresimprinted on the first side of the first substrate. In some embodiments,the process further includes attaching the first and second substratesto each other at the adhesive substance atop the second featuresimprinted on the first side of the first substrate to form a multi-layeroptical device (e.g., the optical device 500). In some embodiments, theprocess further includes attaching the first and second substrates toeach other at the adhesive substance atop the second features imprintedon the first side of the first substrate to form the gap between thefirst substrate and the adjacent surface defined by the secondsubstrate. In some embodiments, the process further includes defining alayer of air between the first and second substrates with a thicknessthat is determined by heights of the second features such that themulti-layer optical device has alternating indexes of refraction.

Advantageously, the process 600 can be used to imprint amulti-functional (e.g., any of functional, anti-reflective, and spacing)3D structure in a single step (e.g., via a single patterning mold) atambient conditions (e.g., at an ambient temperature and at an ambientpressure) that reduces a complexity, a duration, and a cost associatedwith imprinting such 3D structures as compared to producing the 3Dstructures according to other processes. For example, conventionallyformed anti-reflective patterns are deposited under vacuum and can berelatively costly, with spacer components being added in a separate,subsequent process that may include imprinting of large spacerstructures, dispensing of microspheres, or dispensing of curable resistmaterial. Additional time and complexity is associated with cleaning andtreating the anti-reflective pattern prior to performing such a secondprocessing step.

While a number of embodiments have been described for illustrationpurposes, the foregoing description is not intended to limit the scopeof the invention, which is defined by the scope of the appended claims.There are and will be other examples, modifications, and combinationswithin the scope of the following claims.

What is claimed is:
 1. An imprint lithography method of configuring amultilayer wearable eyepiece, the imprint lithography method comprising:imprinting a functional pattern comprising first features of a firstsize range respectively at first locations on a side of a substrateusing shallow features of the first size range of a patterning templateto yield a first waveguide, the first waveguide comprising firstdiffraction gratings configured to project light of a first wavelengthrange and to focus a virtual image at a first depth plane, wherein thefirst diffraction gratings comprise a first incoupling grating and forma first orthogonal pupil expander region and a first exit pupil expanderregion; and while imprinting the functional pattern, imprinting anauxiliary pattern surrounding the functional pattern, the auxiliarypattern comprising: additional first features of the first size range,wherein the additional first features comprise anti-reflective features;and second features of a second size range respectively at secondlocations spaced laterally apart from the first locations on the side ofthe substrate using deep features of the second size range of thepatterning template, the second size range being at least an order ofmagnitude greater in size than the first size range, and the secondfeatures being sized and arranged to define a gap of the second sizerange between the first waveguide and a second waveguide; curing thefirst features, the additional first features, and the second features;and attaching the first waveguide to the second waveguide along thesecond features to define the gap between the first waveguide and thesecond waveguide, thereby yielding at least a portion of the multilayerwearable eyepiece, the second waveguide comprising second diffractiongratings configured to project light of a second wavelength range and tofocus the virtual image at a second depth plane, wherein the seconddiffraction gratings comprise a second incoupling grating and form asecond orthogonal pupil expander region and a second exit pupil expanderregion.
 2. The imprint lithography method of claim 1, wherein the secondfeatures comprise spacers on the side of the substrate.
 3. The imprintlithography method of claim 2, further comprising imprinting one or bothof the spacers and the anti-reflective features along a peripheral edgeof the side of the substrate.
 4. The imprint lithography method of claim2, further comprising imprinting one or both of the spacers and theanti-reflective features within an interior region of the side of thesubstrate.
 5. The imprint lithography method of claim 1, wherein theside of the substrate is a first side of the substrate, the imprintlithography method further comprising imprinting third features of thefirst size range on a second side of the substrate.
 6. The imprintlithography method of claim 5, wherein imprinting the third featurescomprises forming diffraction gratings or anti-reflective features onthe second side of the substrate.
 7. The imprint lithography method ofclaim 1, wherein the second size range comprises a micrometer range ofone or both of about 1 μm to about 50 μm in height of the secondfeatures and about 1 μm to about 100 μm in width of the second features.8. The imprint lithography method of claim 1, wherein the first sizerange comprises a nanometer range of up to about 300 nm in height of thefirst features.
 9. The imprint lithography method of claim 1, furthercomprising imprinting the second features on opposite lateral sides ofthe first features.
 10. The imprint lithography method of claim 1,further comprising creating the patterning template from a predecessormold.
 11. The imprint lithography method of claim 10, further comprisingforming the deep features of the second size range in the predecessormold.
 12. The imprint lithography method of claim 10, further comprisingforming the shallow features of the first size range in the predecessormold.
 13. The imprint lithography method of claim 1, further comprisingaligning the first and second substrates with each other.
 14. Theimprint lithography method of claim 1, further comprising dispensing anadhesive substance atop the second features imprinted on the side of thefirst substrate.
 15. The imprint lithography method of claim 14, furthercomprising attaching the first and second substrates to each other atthe adhesive substance atop the second features imprinted on the side ofthe first substrate to form the gap between the first substrate and theadjacent surface defined by the second substrate.
 16. The imprintlithography method of claim 15, further comprising respectivelyattaching the first and second substrates to each other with a sealalong first and second peripheral edges of the first and secondsubstrates.
 17. The imprint lithography method of claim 1, wherein thegap provides a low index region.
 18. The imprint lithography method ofclaim 17, wherein the low index region comprises air with an index ofrefraction of
 1. 19. The imprint lithography method of claim 1, whereineach of the second features is spaced laterally apart by at least about5 μm to about 100 μm from each of the first features.
 20. The imprintlithography method of claim 1, wherein at least one of the firstwavelength range and the second wavelength range corresponds to redlight with wavelengths in a range of about 560 nm to about 640 nm, greenlight with wavelengths in a range of about 490 nm to about 570 nm, orblue light with wavelengths in a range of about 390 nm to about 470 nm.21. The imprint lithography method of claim 1, wherein the first depthplane and the second depth plane are the same.
 22. The imprintlithography method of claim 1, wherein the second features are spacedlaterally apart from the additional first features on the side of thesubstrate.
 23. The imprint lithography method of claim 22, wherein thesecond features are located about 5 μm to about 100 μm from theadditional first features.